This warning is really annoying.

This allows to write separate tests for the library.

This allows tests to depend on the library, leading to shorter compile times
cleaner boundaries.

This will allow to use multiple internal libraries, which can be used to add
tests for other executables than the main one.

Unfortunately, cabal-doctest is currently not supported in combination with
internal libraries and so I had to temporarily disable doctests.

Brings the "Running" section up to date and mentiones the new flag
"benchmark-generators"

This speeds up the build process of the main copar executable and doesn't
require as much dependencies.

As more and more benchmark suite generators are created, results published and
the tools forgotten, this creates an unnecessary burden on the everyday compile
cycle.

It was still refering to the old syntax.

Rationals were already supported, but their input syntax was the same as for
reals: Decimal fixed point notation. This is now fixed and the functor X^-
allows weights to be written as either integers or ratios of integers, separated
by a slash.

According to stackage.org, 13.11 should be the last LTS release with GHC 8.6.3,
but strangely that also uses 8.4.4. The now selected 13.10 should really depend
the older GHC.